Lieberstein played Toby Flenderson on The Office, as the soft-spoken doormat who served as Head of Human Resources at Dunder Mifflin. In addition to the Golden Globe-winning comedy, Lieberstein has numerous producing credits including The Newsroom, The Bernie Mac Show, The Drew Carey Show, King of the Hill, and others.

More recently, he made his directorial debut with the Song of Back and Neck in which he also stars opposite Rosemarie Dewitt. On the TV side, he serves as showrunner of the Fox sci-fi comedy Ghosted starring Adam Scott and fellow Office alum Craig Robinson.

Lieberstein made the move to ICM from CAA. He continues to be repped by 3 Arts and attorney Ken Richman.